Biopolymers

Biological Hierarchy

  • Molecules form cells
  • cells form tissues
  • tissues form organs
  • organs form organisms
  • organisms form a population
  • populations form species
  • species form a biosphere

Lipids

  • The ones that attach to the cell membrane have an organic group, a phosphate group before the glycerol and saturated fatty acid and unsaturated fatty acid
  • The ones with only saturated fatty acids are closely packed and form a decent cell membrane bilayer
  • The ones that are unsaturated have bent strands and that causes them to be loosely packed
  • Pasted image 20250807105751.png
  • the above is the actual phospholipid bilayer structure
  • The one strand that is unsaturated keeps the bilayer flexible
  • Sterol molecules separate phospholipid bilayers:
  • Pasted image 20250807110117.png

Carbohydrates

  • starch polymer is formed from glucosePasted image 20250807110709.png
  • We've covered this elsewhere

Nucleic acid

  • Inside the cell theres a nucleus
  • Inside the nucleus, there are chromosomes
  • Inside the chromosomes, there are coiled chromatins
  • Inside the coiled chromatin there are DNA double helix
  • Pasted image 20250807110932.png
  • DNA is basically a polyelectrolyte since it has a negative charge. Histones are used to neutralise this negative charge
  • The negative charge is formed due to phosphates

Proteins

  • Amino Acids - Pasted image 20250807112326.png
  • The amino acids basic structure is basically the same. They only vary in R
  • There are a minimum of 2 pKa for this. One of them is in the range of 9-10 and the other is 2-3, This is because of the two functional groups. The 9-10 one is of the NH2 group and the 2-3 one is for the COOH
  • Zwitterionic is when both charges are present on the molecule
  • Each protein has a name, structure, three letter code, one letter code and functional group
  • For example: Tyrosine, Tyr, Y, aromatic, hydroxyl
  • Pasted image 20250807112816.png
  • If the R group is simply one hydrogen, you get Glycine
  • If it's methyl, you get alanine
  • If it's isopropyl, you get valine
  • If it's isobutyl, you get leucine
  • Pasted image 20250807113107.png
  • Simple phenyl group, you get phenylalanine
  • methanol, you get Serine
  • Pasted image 20250807113244.png
  • In professors ppt, the polar molecules are just limited to serine, threonine, tyrosine, asparagine and glutamine. The others, which are given in our polar section are in the non polar section
  • So Glycine, Cysteine are non polar
  • Cystine is basically two cysteines linked together
  • Disulfides are very temperature stable
  • Isoelectric point is the pH where the net charge on the molecule is 0
  • It lies between pK1 and pK2

Peptide bonds

  • two amino acids can combine and form peptide bonds between themselves
  • Pasted image 20250807115338.png
  • pheylalanine, cysteine, glycine would be:
  • Pasted image 20250807115757.png
  • FCG is the code for the protein here
    • Phe Cys Gly
  • The ends of the polypeptide chain are called the amine terminus and carboxy terminus

Function of Proteins

- Enzymes - biological catalyst
- Regulators of catalysis - hormones
- Transport and store O2, metal ions, sugars, lipids, etc
- Contractile Assemblies - muscle fibers, separation o chromosomes, etc
- Sensory - Rhodopsin, nerve proteins
- Cellular defense - immunoglobins, antibodies, killer T cell, receptors
- Structural - collagen, silk, etc.
  • The function of the protein is determined by the protein structure

Protein structure

  • The secondary structure: alpha helix, beta sheets, random coils and beta turns
  • Pasted image 20250807121327.png
  • alpha helix ^
  • Pasted image 20250807121409.png
  • Tertiary structure forms because the side chains "don't like water". t's the 3D structure of an entire peptide
  • Quarternary structure is how the tertiary structures come together